Reciprocating combustion engines are known for converting chemical energy from a fuel source into reciprocating or rotating shaft power. In reciprocating engines, gas is compressed within a cylinder volume defined by a piston, an inner cylinder wall, and a cylinder head, thereby increasing both the pressure and temperature of the gas, where the gas may include a fuel, an oxidizer such as air, or combinations thereof, for example. In spark ignition engines, fuel and oxidizer are premixed upstream of the cylinder volume or within the cylinder volume, such that ignition of the premixed fuel and oxidizer is initiated by arcing an electrical spark across a gap within the cylinder volume. In compression ignition engines, a fuel-oxidizer mixture within the cylinder volume autoignites in response to a time history of temperature and pressure within the volume. More particularly, in direct injection compression ignition engines, fuel is injected into the cylinder volume near the peak of the compression cycle and ignition of the fuel and oxidizer occurs after an autoignition delay time. Heat released from combustion of the fuel-air mixture does work against the piston, which conventionally transfers the work to a rotating crankshaft through a connecting rod.
Canadian Patent Publication 2,178,012 (hereinafter “the '012 publication”), entitled “Piston,” purports to address the problem of reducing combustion emissions from a reciprocating internal combustion engine. The '012 publication describes a piston with a combustion chamber in its upper surface. The combustion chamber in the '012 publication is generally cylindrical with radiused upper edges and lower edges, where the walls of the chamber meet the base of the chamber. However, the combustion chamber arrangement described in the '012 publication ties the depth of the combustion chamber to a selection of a target squish band area on a top surface of the piston and a target compression ratio, thereby limiting the geometrical degrees of freedom available to achieve other target engine metrics.
Accordingly, there is a need for an improved piston that provides geometrical degrees of freedom for satisfying target engine metrics.